A commonly used technique to reduce the amount of scattered X-rays in computed radiography, digital radiography as well as classical film-based X-ray systems is the use of anti-scatter grids. These grids are lead foil strips, placed apart at a certain distance in a suitable covering.
There exist different types of anti-scatter grids. In parallel grids, the lead foil strips are parallel, while in honeycomb grids the strips are placed in a honeycomb pattern. The grids are stationary or moving. The use of these grids effectively reduces the radiation scattering but occasionally introduces artefacts such as grid lines into the image.
In a moving system, the motion of the grids removes the grid lines in the image. However, in some circumstances e.g. short exposure time or malfunctioning of the system, the artefacts remain in the image.
If the image is formed digitally or converted afterwards to a digital image representation, Moiré artefacts may appear when displaying the image at a certain scale. These low frequent Moiré artefacts are mostly disturbing and should be eliminated. Before displaying the image, the grid lines, if present in the image, should be removed.
It is a goal of the present invention to eliminate of the negative influence of periodic artefacts e.g. moiré artefacts of zoomed images, without removing diagnostic information.